Back Bell 533
1962

Bell 533

In 1959, the TRECOM (United States Army's Transportation Research Command) set up a programme in order to determine various rotor systems and methods of drag reduction for helicopters. As a result Bell modified the first YH-40-BF service test model (s/n 56-6723) as a research test-bed which was known at Bell as the Model 533. A lot of reworking was done on the airframe in order to reduce drag. These refinements included a cambered vertical tail surface to unload the tail rotor, streamlined fairing for the rotor head, flush air intakes located on each side of the new rotor fairing, redesigned cross-tubes for landing skids and new hinges for the doors. The well-known stabilising bar was removed and replaced by a variable-tilt rotor mast in order to maintain the fuselage in low-drag attitude. The 1.400shp Lycoming T53-L-13 turboshaft was retained.

Tests in NASA's Ames wind tunnel showed that the aerodynamics of the airframe had been improved to such an extent that the equivalent flatplane area of the Huey had been reduced from 2.3m2 to 1m2. Still with its original US Army serial number, the Model 533 made its maiden flight on Friday 10 August, 1962, and flight tests were conducted at Fort Worth in late 1962. In March 1963, the Model 533 flew at 278km/h and 302km/h was attained in a shallow dive. As the months went by more and more modifications were introduced in this helicopter. Several rotor types were tested (two-blade UH-1B-like rotor and rigid three-blade rotors) and two 765-kg Continental J69-T-9 turbojets were installed on each side of the fuselage. Take-off weight of the aircraft was now 3880kg. On 17 January, 1964, the helicopter achieved a speed of 338km/h in level flight using only 780shp from the 1.100shp Lycoming T53-L-9A shaft-turbine, plus 568kg from the J69s.

The next modification consisted of fitting two small sweptback fixed wings to convert the aircraft into a compound helicopter. On 11 May, 1964, it flew at 357km/h. The aircraft was then flown to San Antonio to have its J69-T-9s replaced by 765-kg J69-T-29s, and, on 15 October, 1964, the Model 533 was the first helicopter to break the 200 knots (370km/h) barrier by attaining 380km/h. On 6 April, 1965, the Model 533 flew at 402km/h in level flight and 409km/h in a shallow dive. It showed also its outstanding manoeuvrability in performing 2g turns and 60deg banks at speeds around 320km/h, and a Mach number of 0.985 was recorded by the advancing blades of the rotor.

Early in 1968, a subsequent phase of the programme was the installation of two 1490-kg Pratt & Whitney JT12A-3 turbojets at the end of short stub wings. The first flight in this configuration was made in 1968, the machine gradually recording still higher speeds and, in May 1969, Bell announced that 508km/h had been attained.

A.J.Pelletier "Bell Aircraft since 1935", 1992

The fourth YH-40-BF was converted to become the Bell Model 533 experimental aircraft in order to test various rotor systems

Model 204 with experimental drag reduction mods including raised rotor mast fairings and flush air intakes, streamlined skids, recontoured fin with starboard side tailplane, twin externally mounted 765kg Continental J69-T9 turbojets and fixed wings for compound high speed flight tests. Prot. s/n 56-6723. FF 10 Aug. 1962.

R.Simpson "Airlife's Helicopter and Rotorcraft", 1998

Late in its career, the Model 533 was fitted with two small wings


Photo Gallery 

In this photo the aircraft has jet pods mounted on either side of the fuselage, thin, swept-back wings, and a standard two-bladed main rotor. Note the rotor housing pylon

Technical data for Model 533

Rotor diameter: 13.41m, length of fuselage: 12.98m, normal take-off weight: 4173kg, maximum speed: 509km/h

Comments 
polo, e-mail, 16.06.2011

The helicopter was repainted some 10 years Orange and White.

Vincent Mbah . C, e-mail, 26.10.2010

Why is this helicopter Bell 533 not rated or recorgnized as the world fastest helicopter on the internet?

wholesale laptop battery, e-mail, 01.06.2010

In 1959, the TRECOM (United States Army's Transportation Research Command) set up a programme in order to determine various rotor systems and methods of drag reduction for helicopters. As a result Bell modified the first YH-40-BF service test model (s/n 56-6723) as a research test-bed which was known at Bell as the Model 533. A lot of reworking was done on the airframe in order to reduce drag. These refinements included a cambered vertical tail surface to unload the tail rotor, streamlined fairing for the rotor head, flush air intakes located on each side of the new rotor fairing, redesigned cross-tubes for landing skids and new hinges for the doors. The well-known stabilising bar was removed and replaced by a variable-tilt rotor mast in order to maintain the fuselage in low-drag attitude. The 1.400shp Lycoming T53-L-13 turboshaft was retained.

Tests in NASA's Ames wind tunnel showed that the aerodynamics of the airframe had been improved to such an extent that the equivalent flatplane area of the Huey had been reduced from 2.3m2 to 1m2. Still with its original US Army serial number, the Model 533 made its maiden flight on Friday 10 August, 1962, and flight tests were conducted at Fort Worth in late 1962. In March 1963, the Model 533 flew at 278km/h and 302km/h was attained in a shallow dive. As the months went by more and more modifications were introduced in this helicopter. Several rotor types were tested (two-blade UH-1B-like rotor and rigid three-blade rotors) and two 765-kg Continental J69-T-9 turbojets were installed on each side of the fuselage. Take-off weight of the aircraft was now 3880kg. On 17 January, 1964, the helicopter achieved a speed of 338km/h in level flight using only 780shp from the 1.100shp Lycoming T53-L-9A shaft-turbine, plus 568kg from the J69s.

The next modification consisted of fitting two small sweptback fixed wings to convert the aircraft into a compound helicopter. On 11 May, 1964, it flew at 357km/h. The aircraft was then flown to San Antonio to have its J69-T-9s replaced by 765-kg J69-T-29s, and, on 15 October, 1964, the Model 533 was the first helicopter to break the 200 knots (370km/h) barrier by attaining 380km/h. On 6 April, 1965, the Model 533 flew at 402km/h in level flight and 409km/h in a shallow dive. It showed also its outstanding manoeuvrability in performing 2g turns and 60deg banks at speeds around 320km/h, and a Mach number of 0.985 was recorded by the advancing blades of the rotor.

Early in 1968, a subsequent phase of the programme was the installation of two 1490-kg Pratt & Whitney JT12A-3 turbojets at the end of short stub wings. The first flight in this configuration was made in 1968, the machine gradually recording still higher speeds and, in May 1969, Bell announced that 508km/h had been attained.

A.J.Pelletier "Bell Aircraft since 1935", 1992

The fourth YH-40-BF was converted to become the Bell Model 533 experimental aircraft in order to test various rotor systems

Model 204 with experimental drag reduction mods including raised rotor mast fairings and flush air intakes, streamlined skids, recontoured fin with starboard side tailplane, twin externally mounted 765kg Continental J69-T9 turbojets and fixed wings for compound high speed flight tests. Prot. s/n 56-6723. FF 10 Aug. 1962.

R.Simpson "Airlife's Helicopter and Rotorcraft", 1998

Late in its career, the Model 533 was fitted with two small wings


Photo Gallery


In this photo the aircraft has jet pods mounted on either side of the fuselage, thin, swept-back wings, and a standard two-bladed main rotor. Note the rotor housing pylon

Technical data for Model 533

Rotor diameter: 13.41m, length of fuselage: 12.98m, normal take-off weight: 4173kg, maximum speed: 509km/h

Comments
John Quackenbush, e-mail, 06.04.2010

Wasn't Mike Kawa from Bell Engineering involved in some of the testing of this aircraft?
Leo Norman, e-mail, 18.02.2010

This machine has a much deeper history than what is listed here.

It was first Air Force contracted (1956) as a YH-40 for the U. S Army as Ship #4. The XH-40's, ships 1, 2, & 3, had an aft C. G. problem which was solved by adding a fuselage 12"forward extension at the cockpit door posts moving the cockpit forward! A correction that helped make the Huey the true utility machine that it has become.
The XH-40's had a design gross weight of 6643 pounds. Please notice final sentence below.

The military agencies discontinued the X & Y model development contracting during this era. This machine, therefore, became the first HU-1 which is the proper Air Force contracted designation. The HU-1's were the first Hueys used by the U, S. Army.

There was an ugly duckling cartoon strip very popular in the newspapers of the era. The big, fat, ugly baby duckling was named Huey. It wore a diaper & baby bonnet & was into everything, but could successfully do anything.

The Airborne troops who were the first to utilize the n ...

John Quackenbush, e-mail, 06.04.2010

Wasn't Mike Kawa from Bell Engineering involved in some of the testing of this aircraft?

Leo Norman, e-mail, 18.02.2010

This machine has a much deeper history than what is listed here.

It was first Air Force contracted (1956) as a YH-40 for the U. S Army as Ship #4. The XH-40's, ships 1, 2, & 3, had an aft C. G. problem which was solved by adding a fuselage 12"forward extension at the cockpit door posts moving the cockpit forward! A correction that helped make the Huey the true utility machine that it has become.
The XH-40's had a design gross weight of 6643 pounds. Please notice final sentence below.

The military agencies discontinued the X & Y model development contracting during this era. This machine, therefore, became the first HU-1 which is the proper Air Force contracted designation. The HU-1's were the first Hueys used by the U, S. Army.

There was an ugly duckling cartoon strip very popular in the newspapers of the era. The big, fat, ugly baby duckling was named Huey. It wore a diaper & baby bonnet & was into everything, but could successfully do anything.

The Airborne troops who were the first to utilize the new helicopter nicknamed the HU-1 Huey from this, getting into everything, can do anything attitude. Even the. Smilin' Jack Martin cartoon strip got involved with the introduction of the Huey's. When the first airborne troops received the first machines, Smilin' Jack had one with six French SS-11 antitank missles mounted on faired support booms on each side of the fuselage.


The change to the UH-1 designation change came about with the development of the U.S. Army Aviation Engineering & Acquisition System.

This machine was later modified as the first AUH-1B, which had a stabilizer bar fatigue life of 325 hours. As the prototype AUH-1B it was kept in Army test & development work. The stabilizer bar failed in flight & the A/C went thru a severely hard landing. It was subsequently contracted into the Model 533 Program as described above.

But it also has the distinction of being the first production Huey Helicopter & the first in the line of all military & commercial variants, including the Huey Cobra.

The U.S.M.C is still taking delivery of the latest variants where their Cobra has an operating gross weight of 18000 pounds.

Stan Aiton, e-mail, 09.02.2008

Great Story! The Helicopter is at the Aviation Applied Technology Directorate which is located on Fort Eustis which is in Newport News VA. The helicopter was repainted some 10 years Orange and White.

Lou Hartwig, e-mail, 01.12.2006

I was the test pilot that was did all the flight tests on this progect.Walter Sonneborne was the engineer that made this program work.He became a vp in engeneering and I became chief pilot and manager of all flight operations.The aircraft is on display at fort eustes at Norfolk Va.

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